OP, I have gone through a similar experience as this, and overanylzing or not it's definitely right for you to care because you know it's a topic that you have a lot to speak on. Probably same thing with him and snowboarding/skiing. I'm sure if he went on about some crazy elevation he's dropped in or backcountry ride, you would have listened and inquired more about it because there's no point in being intimidated or offput by someone's personal passion that you know nothing about. People always have to 'figure you out' for some reason, and the worst are the one's who make their decision in the middle of dinner.
I will say that even though I'm a guy, it's less gender and more generation. I live in a town that is pretty big by itself, but is even bigger with a good sized D2 school in it. Being out of college for a few years now & single, I notice the dates I go on with people my age who are still in school or just graduated can sour mid-date like this. Might be running, might be something else, but it's like you can't share too much.
Last date I was on, the girl told me that she did competitive band, so instead of making a preconceived judgment on that and obviously steering away from that (not that I was against it, but it's not for me), I asked her more about it because I figured she really enjoyed it if she brought it up. Turns out she travelled for it, played all of instruments I knew nothing of, and in the end it was cool that she had a unique passion that she enjoyed. She told me she was a runner when I met her, so when she asked me about my running I tiptoed around anything that would ward her off. Didn't matter, because once I get the question," So, you're not like, a 'serious' runner, right?", with obvious tones hoping I say no, I know I'm done. It's happened a couple of times too, I don't get it but I feel like it'll be less of a trigger point for people the older I get.
People out there run 70-80 mpw, work, do the little things, and have friends that know nothing about it because it doesn't effect their time together.